Recently enacted environmental and energy regulations are requiring that all storage units that contain hazardous and volatile materials, such as Above Ground Storage Tanks and pipelines, be secondarily contained in order to eliminate the occurrence of leakages into the surrounding environment as the integrity of many of the existing tanks and pipelines have degraded over time due to corrosion or were poorly constructed in the first instance. Therefore, several systems have been developed for creating an impervious secondary containment unit in order that the product does not seep or leak out of the primary storage unit into the surrounding environment. In addition, a number of these regulations also require that leak detection and monitoring systems be employed for maintaining the integrity of the secondary containment units. For example, several systems create a control space, such as an interstice, between the primary and secondary units in which, using a liquid or a pressurized gas, one can detect the presence of leaks within the control space by observing the level of liquid or gas within the control space using one or more sensors, a graduated tube or a pressure-drop switch that is in fluid communication with the control space.
However, many of these systems do not provide a method of installing the secondary containment structure in an already existing tank or other storage means and therefore, the entire tank or storage structure must be replaced with a new secondarily contained structure. As can be appreciated by one of ordinary skill in the art, removing a tank from service so that it may be dismantled and replacing it with a whole new structure causes significant disruption and expense, particularly when dealing with hazardous materials. Thus, several systems have been developed for retrofitting an existing tank or storage unit with a secondary containment structure. Unfortunately, most of these retrofit systems begin with standard pre-cut pieces of steel or other material that are imprecise for the layout of the tank. The tanks usually have several protrusions or obstacles such as sumps, pumps, pipes, nozzles, critical welds, roof supports, or manways that cannot be obstructed by the secondary containment structure. In order to accommodate these obstacles and the dimensions of the tank, the pieces are just cut ad-hoc in places where the pieces are inaccurate after installation. This results in an inefficient and imprecise method of creating the secondary containment system. Therefore, there exists a need for a secondary containment system that can be configured to an existing tank or storage unit whereby the method of installation takes into consideration the unique layout of the tank or storage unit and points of structural stress within the tank prior to and during the installation.
With regards to the testing and monitoring of leaks between the primary and secondary structures, oftentimes the control space or the interstice of the existing systems is one continuous space and therefore, it is difficult to identify where a detected leak is occurring. As a result, the entire tank must be inspected for the leak or complex and expensive electronic monitoring systems must be used for pinpointing the exact location of the leak for repair. Furthermore, a single leak harmfully permeates the entire control space. Accordingly, there exists a need for the secondary containment system to be geometrically divided such that the origin of a leak can be quickly located and pre-contained before any manual intervention.
In addition, testing and repair of the integrity of the secondary containment structure does not ordinarily occur until the entire structure has been installed. The installation crew must clear the tank before a qualified technician can enter the tank with a mass spectrometer to conduct the testing. Where welds are used to install the secondary containment structure to the existing tank surface, testing the welds in this fashion results in at least one day of lost productivity per test without any direct feedback to the welders who have performed the work. If leaks are found, the welders must repair the leaks, clear the tank and have the testing process repeated. This cyclical process could be repeated 3 to 5 times before the installation passes a quality inspection. Since the typical installation is about 12 days, the addition of 3 to 5 days for testing is a significant amount of time, resources and expense. Thus, there exists a need for an accurate and simple test-as-you-go method for testing the integrity of the secondary containment structure that does not require the use of expensive, cumbersome and technical equipment and does not require that the crew complete installation before the testing can begin. As a result, repairs can be made on the spot and the crew can identify the defects in their techniques early on in the installation process thereby minimizing installation costs and improving the predictability of the system's integrity.